This invention relates generally to improvements in processes for tanning animal hides or skins to produce leather. More specifically, this invention relates to an improved tanning process for producing washable leather which can be washed repeatedly in water without significant degradation of desirable soft and compliant characteristics.
In general terms, tanning processes have been known for many centuries to produce leather products by dressing and preserving animal hides or skins. Such processes have been utilized in many variations to produce a wide range of useful products, such as apparel items, footwear, upholstery, sports equipment, saddlery, and many other items The particular item to be produced is related directly to the animal skin type and grade together with the specific sequence of process steps employed to obtain a desired set of physical characteristics, such as softness, compliance, durability, etc.
More specifically, in accordance with modern leather tanning processes, selected freshly split animal hides or skins are initially cured typically by salting and/or drying to prevent decay. These skins are subjected to pretanning procedures to remove loose flesh and excess hair, typically by soaking in a water bath including assisting chemical additives. The thus pretreated skins, commonly referred to as pelts, are then bated by soaking in an appropriate solution formulated to soften the pelts and further to remove excess proteins and to improve color. In some cases, fatty substances are leached out by additional soaking in solvent and/or detergent based solutions. The pelts are then chemically treated in vats with selected tanning agents of vegetable or mineral origin for conversion into leather. After tanning, the leather is frequently treated with oils or fats or other lubricating agents to obtain soft and supple characteristics, followed by appropriate dyeing, drying, and finishing.
Although leather products are used for many different types of apparel, it is well known that cleaning of dirt, stains, etc. from a leather garment can be difficult or impossible. That is, leather products have not satisfactorily retained desirable soft and compliant characteristics when wetted with water or water-based solutions of the type used for washing traditional woven fabrics. Instead, when wetted, leather products exhibit a tendency to become stiff and/or brittle when dry, with cracks or splits often occurring in response to frequent wetting. Moreover, permanent discoloration and/or stains can occur when the leather product is wetted with water. As a result, cleaning techniques for leather garments have generally been limited to relatively costly dry cleaning procedures wherein nonaqueous cleaning chemicals are used.
In the past, modified leather products have been developed to permit minor contact with water without significant adverse consequences. For example, treated suede leathers have been developed to withstand occasional surface spot cleaning with water-based solutions, with minimal change to surface characteristics or color. Other leather products have been treated during post tanning processes with specialized oil formulations to resist water penetration and damage However, prior leather products have not been developed to withstand repeated washing by full immersion in water in the manner used for cleaning traditional woven fabrics.
The object of this invention, therefore, is to provide an improved leather tanning process designed to produce a washable leather product which can be immersed and washed in water repeatedly and substantially without degradation or change in physical characteristics.